控制系统介绍外文文献翻译、中英文翻译、外文翻译Word格式.docx

控制系统介绍外文文献翻译、中英文翻译、外文翻译Word格式.docx

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tooling,handling,andassemblingmechanicalpartsinthemanufacturingindustries,amongmanyothers.

Sinceadvancesinthetheoryandpracticeofautomaticcontrolprovidemeansforattainingoptimalperformanceofdynamicsystems,improvethequalityandlowerthecostofproduction,expandtheproductionrate,relievethedrudgeryofmanyroutine,repetitivemanualoperationsetc,mostengineersandscientistsmustnowhaveagoodunderstandingofthisfield.

ThefirstsignificantworkinautomaticcontrolwasJamesWatt’scentrifugalgovernorforthespeedcontrolofasteamengineintheeighteenthcentury.OthersignificantworksintheearlystagesofdevelopmentofcontroltheorywereduetoMinorsky,Hazen,andNyquist,amongmanyothers.In1922Minorskyworkedonautomaticcontrollersforsteeringshipsandshowedhowstabilitycouldbedeterminedbythedifferentialequationsdescribingthe system.In1934Hazen, whointroducedtheterm“ervomechanisms”forpositioncontrolsystems,discusseddesignofrelayservomechanismscapableofcloselyfollowing

achanginginput.

Duringthedecadeofthe1940’s,frequency-responsemethodsmadeitpossibleforengineerstodesignlinearfeedbackcontrolsystemsthatsatisfiedperformancerequirements.Fromtheendofthe1940’stoearly1950’s,theroot-locusmethodincontrolsystemdesignwasfullydeveloped.

Thefrequency-responseandtheroot-locusmethods,whicharethecoreofclassicaltheory,leadtosystemsthatarestableandsatisfyasetofmoreorlessarbitraryperformancerequirements.Suchsystemsare,in

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general,notoptimalinanymeaningfulsense.Sincethelate 1950’s,theemphasisoncontroldesignproblemshasbeenshiftedfromthedesignofoneofmanysystemsthatcanworktothedesignofoneoptimalsysteminsomemeaningfulsense.

Asmodernplantswithmanyinputsandoutputsbecome moreandmorecomplex,thedescriptionofamoderncontrolsystemrequiresalargenumberofequations.Classicalcontroltheory,whichdealsonlywithsingle-input-single-outputsystems,becomesentirelypowerlessformultiple-input-multiple-output systems. Since about 1960, moderncontroltheoryhasbeendevelopedtocopewiththeincreasedcomplexityofmodernplantsandthestringentrequirementsonaccuracy,weight,andindustrialapplications.

Becauseofthereadilyavailableelectronicanalog,digital,andhybridcomputersforuseincomplexcomputations,theuseofcomputersinthedesignofcontrolsystemsandtheuseofon-linecomputersintheoperationofcontrolsystemsarenowbecomingcommonpractice.

Themostrecentdevelopmentsinmoderncontroltheorymaybesaidtobeinthedirectionoftheoptimalcontrolofbothdeterministicandstochasticsystemsaswellastheadaptiveandlearningcontrolofcomplexsystems. Applicationsof modern controltheory tosuchnonengineeringfieldsasbiology,economics,medicine,andsociologyarenowunderway,andinterestingandsignificantresultscanbeexpectedinthenearfuture.

Nextweshallintroducetheterminologynecessarytodescribe

controlsystems.

Plants.Aplantisapieceofequipment,perhapsjustasetofmachinepartsfunctioningtogether,thepurposeofwhichistoperformaparticularoperation.Hereweshallcallanyphysicalobjecttobecontrolled（suchasaheatingfurnace,achemicalreactor,oraspacecraft）aplant.

Processes.TheMerriam-WebsterDictionarydefinesaprocesstobe

anatural,progressivelycontinuingoperationordevelopmentmarkedbyaseriesofgradualchangesthatsucceedoneanotherinarelativelyfixedwayandleadtowardaparticularresultorend;

oranartificialorvoluntary,progressivelycontinuingoperationthatconsistsofaseriesofcontrolled

actionsormovementssystematicallydirectedtowardaparticularresultorend.Hereweshallcallanyoperationtobecontrolledaprocess.Examplesarechemical,economic,andbiologicalprocess.

Systems.Asystemisacombinationofcomponentsthatacttogetherandperformacertainobjective.Asystemisnotlimitedtoabstract,dynamicphenomenasuchasthoseencounteredineconomics.Theword“system”should,therefore,beinterpretedtoimplyphysical,biological,economic,etc.,system.

Disturbances.Adisturbanceisasignalwhichtendstoadverselyaffectthevalueoftheoutputofasystem.Ifadisturbanceisgeneratedwithinthesystem,itisca